From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: stable@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	patches@lists.linux.dev,
	Eric Dumazet <edumazet@google.com>,
	Jakub Kicinski <kuba@kernel.org>,
	Sasha Levin <sashal@kernel.org>
Subject: [PATCH 6.18 0576/1250] drop_monitor: fix size calculations for 64-bit attributes
Date: Thu, 17 Sep 2026 16:06:11 +0100
Message-ID: <20260917151607.511534469@linuxfoundation.org>
In-Reply-To: <20260917151551.901433442@linuxfoundation.org>
References: <20260917151551.901433442@linuxfoundation.org>
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6.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Eric Dumazet <edumazet@google.com>

[ Upstream commit 7089f7ab99c89f443c92d8fcc585e63f2727f0b3 ]

net_dm_packet_report_fill() and net_dm_hw_packet_report_fill() use
nla_put_u64_64bit() to append 64-bit attributes (NET_DM_ATTR_PC and
NET_DM_ATTR_TIMESTAMP).

On 32-bit architectures without CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS,
nla_put_u64_64bit() may append a 4-byte NET_DM_ATTR_PAD attribute for
64-bit alignment.

However, net_dm_packet_report_size() and net_dm_hw_packet_report_size()
used nla_total_size(sizeof(u64)) instead of nla_total_size_64bit(sizeof(u64)),
budgeting 12 bytes instead of up to 16 bytes.

This under-estimation of SKB size can lead to an skb_over_panic() when
__nla_reserve() or skb_put() is subsequently called.

Fix this by using nla_total_size_64bit(sizeof(u64)) in both size calculations.

Fixes: ca30707dee2b ("drop_monitor: Add packet alert mode")
Fixes: 5e58109b1ea4 ("drop_monitor: Add support for packet alert mode for hardware drops")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20260722141743.3266924-2-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 net/core/drop_monitor.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/net/core/drop_monitor.c b/net/core/drop_monitor.c
index 54bf1f60829e8..1383e90735edc 100644
--- a/net/core/drop_monitor.c
+++ b/net/core/drop_monitor.c
@@ -567,13 +567,13 @@ static size_t net_dm_packet_report_size(size_t payload_len)
 	       /* NET_DM_ATTR_ORIGIN */
 	       nla_total_size(sizeof(u16)) +
 	       /* NET_DM_ATTR_PC */
-	       nla_total_size(sizeof(u64)) +
+	       nla_total_size_64bit(sizeof(u64)) +
 	       /* NET_DM_ATTR_SYMBOL */
 	       nla_total_size(NET_DM_MAX_SYMBOL_LEN + 1) +
 	       /* NET_DM_ATTR_IN_PORT */
 	       net_dm_in_port_size() +
 	       /* NET_DM_ATTR_TIMESTAMP */
-	       nla_total_size(sizeof(u64)) +
+	       nla_total_size_64bit(sizeof(u64)) +
 	       /* NET_DM_ATTR_ORIG_LEN */
 	       nla_total_size(sizeof(u32)) +
 	       /* NET_DM_ATTR_PROTO */
@@ -769,7 +769,7 @@ net_dm_hw_packet_report_size(size_t payload_len,
 	       /* NET_DM_ATTR_FLOW_ACTION_COOKIE */
 	       net_dm_flow_action_cookie_size(hw_metadata) +
 	       /* NET_DM_ATTR_TIMESTAMP */
-	       nla_total_size(sizeof(u64)) +
+	       nla_total_size_64bit(sizeof(u64)) +
 	       /* NET_DM_ATTR_ORIG_LEN */
 	       nla_total_size(sizeof(u32)) +
 	       /* NET_DM_ATTR_PROTO */
-- 
2.53.0